The present invention relates to an analyser for wood chips. Such an apparatus is useful in the paper-making industry.
In very general terms, paper is made by mulching chips into a pulp, and then pressing this pulp to extract water and dry it so as to make paper.
The analysis of wood chips is extremely important for the paper industry. Paper mills require that the chips used for making paper have sizes within a predetermined range. If a percentage of the chips lies outside the range, the paper mill can require that the chips producer pay a fine, partly to offset the cost of chemicals necessary to xe2x80x9cdigestxe2x80x9d the offending chips.
There are a few machines that exist to analyse the chips, generally based on the principle of sifting a sample of the load of chips in a number of mechanical sieves having progressively smaller holes or openings. Once the sample has been sieved, weight percentages are established according to the sizes of the sieves. These machines have the distinct disadvantage of not providing accurate results. Furthermore, when the chips are sifted, they can inadvertently be oriented vertically instead of horizontally, which skews the percentages. FIG. 3 shows a typical report generated by a prior art apparatus. As can be seen, the chips are classified according to their length (measured in mm) and their length (here, measured in inches). However, no provision is made for width and for the distribution of thickness of each chip, and it is impossible to ascertain from this report the digestibility index of the load of chips.
It is an object of the present invention to provide a wood chips analyser which provides more accurate results, and which is more flexible than in the prior art.
In accordance with the invention, this object is achieved with a wood chips analyser comprising:
a transparent conveyor for conveying the chips from an upstream position to a downstream position, the transparent conveyor having a top and a bottom surfaces;
means for feeding the chips to the transparent conveyor;
means for spreading the chips on the transparent conveyor;
a pair of cameras, one of the cameras facing the top surface of the transparent conveyor, the other camera facing the bottom surface of the transparent conveyor, both cameras being focused on an imaginary line crossing the transparent conveyor, each camera having an output;
means for receiving the output of each camera and analysing the same in order to categorize the chips according to predetermined criteria and produce an output; and
means for controlling the transparent conveyor, the pair of cameras, the means for feeding the chips, the means for spreading the chips and the means for receiving the output of each camera.